During the past few years, the need for wind tunnel pressure measurement systems with higher data rates has become acute. Currently the need for higher data rates revolves around achieving a more economical operation of these energy intensive facilities through continuous pitch and pitch-pause modes of operations, active tunnel control, and real-time data analysis and display. Higher data rates for pressure measurements are also needed, as they have been in the past, for wind tunnels with short run times. The major obstacle in achieving high data rates from pressure measurement systems has been most often the pressure sensing scheme. Modern computer-based data acquisition systems allow data rates of 50,000 measurements per second (MPS) and greater, yet the electromechanically scanned pressure sensors most often used for wind tunnel pressure measurements allow a maximum data rate of only about 10 MPS. These electromechanically scanned pressure sensors can be paralleled to achieve a somewhat higher data rate, but still not one that is commensurate with that of the data acquisition systems. The use of individual pressure transducers to achieve a high data rate is often impractical because of size requirements and cost.
Some progress in developing pressure sensing concepts with potentially high data rates has been made recently. A miniature 25-channel pressure sensing module consisting of 25 silicon diaphragm pressure sensors mounted to a header plate has been developed. (Mallon, J. R., Kurtz, A. D., and Coe, C., "Twenty-Five Channel Electrically Scanned Solid State Pressure Transducer," Instrument Society of America. Twentieth International Instrumentation Symposium, Albuquerque, NM, May 21-23, 1974). This module allows high data rates since the electrical outputs of the pressure sensors can be electronically scanned. However, this sensor module does not permit a full in situ calibration, therefore corrections for zero and sensitivity shifts usually associated with these sensors cannot be made. Another pressure measurement system (Armentrout, E. C., "On-Line Calibration of High-Response Pressure Transducers During Jet-Enging Testing." Society of Automotive Engineers. National Aerospace Engineering and Manufacturing Meeting, San Diego, CA, Oct. 1-3, 1974) has been developed that allows a full in situ calibration of individual silicon diaphragm pressure sensors, but the system is too large to be mounted in most wind tunnel models. The data rate of this system is generally determined by the lengths of the tubes from the pressure ports to the sensors. Another concept advanced employs miniature pressure switches adjacent to the pressure sensors to allow in situ calibration (U.S. Pat. No. 3,777,546) and in those instances where model size permits, high data rates are possible with this scheme.
It is the primary object of this invention to provide a pressure sensor module that largely overcomes the drawbacks of the above-mentioned systems.
Another object of this invention is to provide a pressure sensor module that is small in size, that has a high data rate and that has high accuracy through a full in situ calibration capability.
A further object of this invention is to provide a pressure measuring system that has a high data rate and an in situ calibration capability.
Other objects and advantages of this invention will become apparent hereinafter in the specification and drawings.